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Número de pieza | LM2717 | |
Descripción | Dual Step-Down DC/DC Converter | |
Fabricantes | National Semiconductor | |
Logotipo | ||
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LM2717
Dual Step-Down DC/DC Converter
General Description
The LM2717 is composed of two PWM DC/DC buck (step-
down) converters. The first converter is used to generate a
fixed output voltage of 3.3V. The second converter is used to
generate an adjustable output voltage. Both converters fea-
ture low RDSON (0.16Ω) internal switches for maximum effi-
ciency. Operating frequency can be adjusted anywhere
between 300kHz and 600kHz allowing the use of small ex-
ternal components. External soft-start pins for each enables
the user to tailor the soft-start times to a specific application.
Each converter may also be shut down independently with its
own shutdown pin. The LM2717 is available in a low profile
24-lead TSSOP package ensuring a low profile overall solu-
tion.
Features
■ Fixed 3.3V output buck converter with a 2.2A, 0.16Ω,
internal switch
■ Adjustable buck converter with a 3.2A, 0.16Ω, internal
switch
■ Operating input voltage range of 4V to 20V
■ Input undervoltage protection
■ 300kHz to 600kHz pin adjustable operating frequency
■ Over temperature protection
■ Small 24-Lead TSSOP package
Applications
■ TFT-LCD Displays
■ Handheld Devices
■ Portable Applications
■ Laptop Computers
Typical Application Circuit
© 2008 National Semiconductor Corporation 200785
20078501
www.national.com
1 page Absolute Maximum Ratings (Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
VIN
SW1 Voltage
SW2 Voltage
FB1, FB2 Voltages
CB1, CB2 Voltages
VC1 Voltage
VC2 Voltage
SHDN1 Voltage
SHDN2 Voltage
SS1 Voltage
SS2 Voltage
−0.3V to 22V
−0.3V to 22V
−0.3V to 22V
−0.3V to 7V
−0.3V to VIN+7V
(VIN=VSW)
1.75V ≤ VC1 ≤ 2.25V
0.965V ≤ VC2 ≤ 1.565V
−0.3V to 7.5V
−0.3V to 7.5V
−0.3V to 2.1V
−0.3V to 2.1V
FSLCT Voltage
Maximum Junction Temperature
Power Dissipation(Note 2)
Lead Temperature
Vapor Phase (60 sec.)
Infrared (15 sec.)
ESD Susceptibility (Note 3)
Human Body Model
AGND to 5V
www.DataSh1e5e0t°4CU.com
Internally Limited
300°C
215°C
220°C
2kV
Operating Conditions
Operating Junction
Temperature Range
(Note 4)
Storage Temperature
Supply Voltage
SW1 Voltage
SW2 Voltage
−40°C to +125°C
−65°C to +150°C
4V to 20V
20V
20V
Electrical Characteristics
Specifications in standard type face are for TJ = 25°C and those with boldface type apply over the full Operating Temperature
Range (TJ = −40°C to +125°C). VIN = 5V, IL = 0A, and FSW = 300kHz unless otherwise specified.
Symbol
Parameter
Conditions
Min
(Note 4)
Typ
(Note 5)
Max
(Note 4)
Units
IQ Total Quiescent Current (both Not Switching
switchers)
Switching, switch open
2.7 6 mA
6 12 mA
VFB1
VFB2
VSHDN = 0V
Fixed Buck Feedback Voltage
Adjustable Buck Feedback
Voltage
9
3.3
1.267
27
µA
V
V
ICL1(Note 6) Fixed Buck Switch Current
Limit
VIN = 8V (Note 7)
2.2 A
ICL2(Note 6) Adjustable Buck Switch
Current Limit
VIN = 8V (Note 7)
3.2 A
IB1
Fixed Buck FB Pin Bias
VIN = 20V
Current
(Note 8)
65 µA
IB2 Adjustable Buck FB Pin Bias VIN = 20V
Current
(Note 8)
65 nA
VIN Input Voltage Range
gm1
Fixed Buck Error Amp
ΔI = 20µA
Transconductance
4 20 V
1340
µmho
gm2 Adjustable Buck Error Amp ΔI = 20µA
Transconductance
1360
µmho
AV1 Fixed Buck Error Amp Voltage
Gain
134 V/V
AV2 Adjustable Buck Error Amp
Voltage Gain
136 V/V
DMAX
FSW
ISHDN1
Maximum Duty Cycle
Switching Frequency
Fixed Buck Shutdown Pin
Current
RF = 46.4k
RF = 22.6k
0V < VSHDN1 < 7.5V
89 93
%
200 300 400 kHz
475 600 775 kHz
−5 5 µA
ISHDN2
Adjustable Buck Shutdown Pin 0V < VSHDN2 < 7.5V
Current
−5
5 µA
5 www.national.com
5 Page www.DataSheet4U.com
FIGURE 1. 15V, 3.3V Output Application
20078558
FIGURE 2. 5V, 3.3V Output Application
11
20078559
www.national.com
11 Page |
Páginas | Total 14 Páginas | |
PDF Descargar | [ Datasheet LM2717.PDF ] |
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